1. Field of the Invention
The invention relates to gas turbine engine combustor top hat cover attachment systems. More particularly, embodiments of the invention incorporate lugged backing plates that interlock with mating recesses formed in the corresponding midframe combustor portal. The top hat cover is in turn fastened to the combustor portal by top hat cover fasteners that engage the corresponding threaded apertures formed in the backing plate.
2. Description of the Prior Art
Referring to FIGS. 1 and 2 an exemplary industrial gas turbine engine 10 is shown. The exemplary engine 10 includes a compressor section 12, a combustor section 14, a turbine section 16, and an exhaust section or system 18. The combustor section 14 includes a plurality of combustors 20 that are arrayed about a combustor midframe 22. Each combustor 20 is communication with the combustor section 14 interior via a corresponding combustor portal 23. Each combustor 20 has a “top hat” cover 24 that is affixed to a combustor portal mating surface 26. The combustor portal mating surface 26 has an array of threaded apertures 27 about its circumference that are aligned coaxially with a top hat flange 28 and its array of corresponding through hole apertures 29. The top hat cover flange 28 is then affixed to combustor portal 23 by passing top hat cover fasteners 30 through the through hole apertures 29, which then engage the corresponding combustor portal mating surface threaded apertures 27.
A typical known engine 10 has sixteen combustors 20. Each typical known combustor top hat cover 24 is affixed to the combustor midframe with twenty-four threaded fasteners. Thus, a typical known gas turbine engine 10 requires formation of approximately 384 threaded apertures 27 during its midframe manufacture. The aperture holes 27 must be drilled with relatively precise coaxial and circumferential alignment, on a large and relatively complex three dimensional midframe 22 fabrication. Each of those drilled holes is then hand threaded. Damage repair of any of the threaded apertures 27 formed in the midframe 22—whether damage is incurred during initial fabrication or discovered during subsequent service inspection of the engine 10—is labor intensive, complex and time consuming. Lost time during service outages potentially delays resumption of the turbine engine 10 power generation operation.